1. Field of the Invention
The present invention relates to a thermal management system of a semiconductor integrated circuit having an on-chip thermo sensor (thermo sensor embedded in a chip).
2. Description of the Related Art
In a highly sophisticated semiconductor integrated circuit, parallel processing, high speed processing and the like advance, and a rise of a chip temperature caused by such advancement becomes a problem.
When the chip temperature is equal to or greater than a limit, a phenomenon such as a transistor breakage or firing occurs, and thus, there is a need for a technique of preventing such a phenomenon.
As one of the above techniques, there is provided a management technique in which a thermo sensor is embedded in a chip, and when a chip temperature exceeds a predetermined value, a cooling fan is driven, a processing speed is lowered, and further, operation is stopped (refer to, for example, Jpn. Pat. Appln. KOKAI Publication No. 10-41466).
According to this method, calibration of adjusting a predetermined temperature for starting the cooling fan is executed before shipment. In the calibration, a trimming value is determined such that an alert is outputted at the predetermined temperature, and this value is stored in a fuse box.
The chip environment which is the predetermined temperature is created by, for example, a plate, oven, and heat bath, controlled in temperature. To obtain an alert output accurately at the predetermined temperature, self-heating by a leak current in a chip needs to be considered (refer to, for example, Jpn. Pat. Appln. KOKAI Publication No. 2003-149055).
However, if a trimming value determined by calibration before shipment is still continued to be used, an alert is outputted at a temperature other than the predetermined temperature originating from aging characteristics of a thermo sensor, a comparator or the like after shipment.